109 lines
4.1 KiB
C#
109 lines
4.1 KiB
C#
using System;
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using System.Collections.Generic;
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using FluidSim.Interfaces;
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namespace FluidSim.Components
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{
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/// <summary>
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/// Zero‑dimensional control volume with arbitrary number of ports.
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/// Integrates mass and energy fluxes from all ports.
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/// Safeguards keep a tiny amount of gas to avoid negative states.
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/// </summary>
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public class Volume0D : IComponent
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{
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public List<Port> Ports { get; } = new List<Port>();
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public double Mass { get; private set; }
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public double InternalEnergy { get; private set; }
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public double Volume { get; set; }
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public double Dvdt { get; set; }
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public double Gamma { get; set; } = 1.4;
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public double GasConstant { get; set; } = 287.0;
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// Ambient pressure used for emergency refill – default 101325 Pa
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public double AmbientPressure { get; set; } = 101325.0;
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// Derived quantities
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public double Density => Mass / Math.Max(Volume, 1e-12);
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public double Pressure => (Gamma - 1.0) * InternalEnergy / Math.Max(Volume, 1e-12);
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public double Temperature => Pressure / Math.Max(Density * GasConstant, 1e-12);
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public double SpecificEnthalpy => Gamma / (Gamma - 1.0) * Pressure / Math.Max(Density, 1e-12);
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public Volume0D(double initialVolume, double initialPressure,
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double initialTemperature, double gasConstant = 287.0, double gamma = 1.4)
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{
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GasConstant = gasConstant;
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Gamma = gamma;
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Volume = initialVolume;
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Dvdt = 0.0;
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double rho0 = initialPressure / (GasConstant * initialTemperature);
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Mass = rho0 * Volume;
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InternalEnergy = (initialPressure * Volume) / (Gamma - 1.0);
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}
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/// <summary>Add a new port and initialise it to the volume's current state.</summary>
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public Port CreatePort()
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{
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var port = new Port { Owner = this };
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// Set the port state immediately to avoid a mismatch before the first integration
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port.Pressure = Pressure;
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port.Density = Density;
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port.Temperature = Temperature;
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port.SpecificEnthalpy = SpecificEnthalpy;
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Ports.Add(port);
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return port;
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}
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/// <summary>
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/// Integrate over dt using the MassFlowRate and SpecificEnthalpy
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/// that have been set on each port during the coupling resolution phase.
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/// </summary>
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public void UpdateState(double dt)
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{
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double totalMdot = 0.0;
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double totalEdot = 0.0;
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foreach (var port in Ports)
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{
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totalMdot += port.MassFlowRate;
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// mdot * h gives energy flow: positive mdot = inflow, negative = outflow
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totalEdot += port.MassFlowRate * port.SpecificEnthalpy;
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}
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double dm = totalMdot * dt;
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double dE = totalEdot * dt - Pressure * Dvdt * dt; // piston work
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Mass += dm;
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InternalEnergy += dE;
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// Safeguards: keep at least 1 µg of gas at a small pressure
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double V = Math.Max(Volume, 1e-12);
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if (Mass < 1e-9)
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{
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Mass = 1e-9;
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InternalEnergy = AmbientPressure * V / (Gamma - 1.0);
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}
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else if (InternalEnergy < 0.0)
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{
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InternalEnergy = AmbientPressure * V / (Gamma - 1.0);
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}
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// Final non‑negative clamps (should not be needed after above)
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if (Mass < 0.0) Mass = 1e-9;
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if (InternalEnergy < 0.0) InternalEnergy = AmbientPressure * V / (Gamma - 1.0);
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// Push updated state back to all ports
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double p = Pressure, rho = Density, T = Temperature, h = SpecificEnthalpy;
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foreach (var port in Ports)
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{
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port.Pressure = p;
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port.Density = rho;
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port.Temperature = T;
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port.SpecificEnthalpy = h; // will be overwritten by couplings for inflow, but this is the default
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}
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}
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IReadOnlyList<Port> IComponent.Ports => Ports;
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}
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} |